DESCRIPTION: There is a high demand in dentistry for ceramics that combine high strength and optical properties matching those of natural teeth, and in reconstructive surgery for bioactive ceramics with improved toughness. Our previous work has led to the development of a novel glass-ceramic that is pressable using conventional laboratory techniques. This material exhibits a textured microstructure and improved toughness. The overall objective of this proposal is to develop a dental glass-ceramic that combines high strength and excellent esthetics. An additional goal is to produce bioactive ceramics with improved toughness. Toughness in textured materials is directly related to the degree of texture and microstructure. Our approach to producing high strength dental ceramics is to optimize the texture, promote the nucleation of a submicroscopic secondary mica phase and reduce flaw density and size in the pressed product. Texture refinement will be achieved via two techniques: heat treatment in a temperature gradient followed by heatpressing or heat treatment of the glass after heat-pressing. Microstructure will be tailored by adding AIPO4 as a nucleating agent. Translucency will be improved by adding La203 to increase the refractive index of the glassy matrix, thereby reducing the mismatch between the indices of crystalline and glassy phases. Reduction in flaw density and size will be achieved by eliminating the surface layer present after pressing and by heat treatment of the pressed ceramic to promote crack healing. Textured bioactive ceramics with improved toughness will be produced via heat pressing. The crystallization behavior and thermal properties will be studied by thermal analysis, XRD and SEM. The degree of texture will be investigated by SEM and XRD. The surface layer will be analyzed by X-ray reflectometry and EDS. The mechanical and optical properties will be measured on textured, non-textured and commercially available ceramics as controls. The experimental design uses an adaptive sampling scheme to optimize the optical and mechanical properties and integrate the different aims. Potential applications include dental restorations, dental implant superstructures, and bone replacement implants.